Guard grating for turbine plants



Aug. 24-, 1943.. Q E DEN I 2,327,703

GUARD GRATING FOR TURBINE PLANTS Filed May 11, 194.0

Car F; ll'p Fvede'n INVE N'rore,

,welding has obviously caused the fractures.

Patented Aug. 24, 1943 In turbine plants guard gratings must be provided to separate from, the motive water solid objects such as twigs, logs, leaves, bark, ice and so on which may have a deleterious effect upon the turbine plant. In order to separate large objects, so-called wreck or coarse mesh gratings are used, which are placed before the turbine intakes. consist of edgewise placed flat irons, so-called grating irons, which are located ata free distance from one another of usually about 7 to 10 cm. i To prevent small objects and fish from passing the turbines so-called fine mesh gratings with a free distance of about to mm. between the grating irons are provided behind the coarse mesh gratings.

The abovementioned guard gratings or twig gratings have generally beenmanufactured in such a way that a bolt has been inserted in corresponding holes made in the grating irons and that the grating irons are held at fixed distances from one another by tube pieces pushed on to the bolt and provided between the different grating irons, the said tube pieces being cut into pieces corresponding to the free openings in question. This method is very troublesome andhas proved to involve the drawback that at the flowing through of the water all parts of the twig grating begin to vibrate, which at times may be quite serious so that after a relatively short time the bolts are eaten away and burst.

To prevent these drawbacks, one has tried to weld the grating irons to the bolts. This method is expensive, and, moreover, it has appeared that twig gratings manufactured in this way have burst at violent flow of water. The local heating to which the iron has been subjected at the To eliminate this drawback by bringing the iron to a red heat would, in view'o-f the dimensions, as a rule become diflicult as well as expensive.

The said coarse mesh gratings generally The abovementioned drawbacks are removed by the present invention, and the invention is substantially characterised by the fact that in the grating irons corresponding holes are bored in which are inserted relatively thick-walled tubes, whereafter the grating irons are placed at suitable distances from one another on the tubes, and that a mandrel is drawn through claim as new and desire to secure by Letters the tubes, and that the said rod is cast on to the tube by lead or some other metallic intermediate layer capable of moderating vibrations and shocks.

An example of a twig grating manufactured according to the present method is illustrated on the accompanying drawing, in which Fig. 1 isa View in plan of a twig grating,

Fig. 2 a section along the line 11-11 of Fig. 1, and Fig. 3 a section analogous with that of Fig. 2, the grating irons having another shape.

The reference numeral 2 indicates the grating irons which are usually made of flat irons, see Fig. 2, but may, of course, be of any suitable shape, see Fig. 3. The grating irons are held together by tubes 3 having a diameter which preferably is so large that they just may be inserted in holes bored in the grating irons. The grating irons are placed at that distance from one another on the tubes, which they are to have when the grating is ready, whereafter a mandrel (not shown in the drawing) is drawn through the tubes, said mandrel pressing out the material of the tube so that the outer diameter D of the tube will be larger than the diameter d of the holes made in the grating irons, whereby the grating irons will be effectively locked on to the tubes. During the drawing operation the grating irons are preferably retained in the fixed positions by suitable means. It has appeared that suitable expansion may be obtained in one drawing. To prevent formation of rust on the inside of the tubes, either a protecting layer of paint may be provided thereon, for example by drawing a bunch of rags soaked with paint through the tube, or the ends of the tubes may be shut up by welding or screws.

To enlarge the mechanical strength of the tubes, there may in the ready drawn tube be inserted a metal rod 4 around which is cast a relatively soft and easily fusible metal 5, such as lead, which has the faculty of moderating vibrations and shocks. By providing suitable flutes or other patterns in the surfaceof the metal rod theadhesive faculty of the cast-in metal is considerably increased.

According to this method twig'gratings may be benches and thenbe cut intosections having a width of for example 800 mm.-which is suitable for transport,-mounting and inspection.

Having now described my invention, what I Patent is:

1. A guard grating for turbine plants, comprising grating irons and transverse irons to which the grating irons are fixed, said transverse irons consisting of relatively thick walled tubes passing through openings in the grating irons and spacing the latter one from the other, said tubes being provided with enlargements between the grating irons to retain the latter on the tubes, each tube having inserted therein elongated reinforcing means elastically secured to the inner wall of the tube.

2. A guard grating for turbine plants, comprising grating irons and transverse irons to which consisting of relatively thick walled tubes passing through openings in the grating irons and spacing the latter one from the other, saidtubes being 7 provided with enlargements between the grating irons to retain the latter on the tubes, each tube metal whereby said rod is being cast into said tube, said layer of soft metal being capabl of moderating vibrations and shocks.

3. A guard grating, as claimed in claim 2, in

which each reinforcing rod is provided on its surface with incisions patterned to increase the adhesion of said soft metal layer to said rod surface.

4. A guard grating for turbine plants, comprising grating irons and transverse irons to which the grating irons are fixed, said transverse irons consisting 'ofrelatively thick walled tubes passing through openings in the grating irons and the grating irons are fixed, said transverse irons 1 spacing the latter one from e other. s tubes beingprovided with enlargements between the grating irons to retain the latter on the tubes.

' 5. A guard grating, as claimed in claim 2, com-- prising closures secured to the ends of the tubes metallayers.

' 'to prevent axial displacement of the rods and CARL 'FILIP FREDEN. 

